Luminaire lens



V. S. WlNCE Dec. 9, 1969 LUMINAIRE LENS Z5 Sheets-Sheet 1 Filed Nov. 1.1966 2 c S R W Y WWW E W Mm MM? f v. s. WINCE LUMINAIRE LENS Dec. 9,1969 3 Sheets-Sheet 2 Filed Nov. 1, 1966 mvzm'on VIE/9%; ,Si M/WEATTORNEYS Dec. 9, 1969 v. s. WXNCE 3,483,366

LUMINAIRE LENS 3 Sheets-Sheet 3 Filed Nov. 1, 1966 INVENTOR VEAWA ,5.M/VCZ BY 7WW ATTORNEYS United States Patent US. Cl. 240-106 8 ClaimsABSTRACT OF THE DISCLDSURE A refractor lens for use with a linear lightsource is provided and which utilizes a unique combination of linear andpoint apexed cut-off prisms for control of both longitudinal andtransverse components of light from the linear source. A row of pointapexed light cutoff prisms are disposed substantially directly below thelinear light source and rows of line apexed cut-01f prisms are disposedon either side of the row of point apexed prisms and extend in pathstransversely of the axis of the linear light source. The results aresuch that a much wider transverse light distribution is effected ascompared to similar luminaire units because of the use of the linearcut-off prisms. A variation in longitudinal light transmission from theincident surface to the linear cut-off prisms and a variation inreflection at the light emitting surfaces of the linear cut-off prismscauses a variation in light distribution in the longitudinal andtransverse directions below the units. Because of the total reflectionof light by the sides of the linear apexed cut-off prisms, small conicalcut-off prisms with oval bases are disposed in the valleys between suchprisms and are so oriented that the greatest projected area of lightemission extends in the longitudinal direction. The ends of therefractor lens may be provided with point apexed cut-off prisms tobrighten up the end portions of the luminaire where opaque socket andfixture elements normally create dark areas.

The present invention relates to luminaires, and more particularly to arefractor lens for use in a luminaire. Such luminaires can be recessedin a ceiling, or mounted exposed, on or below the ceiling. With eithertype, there is usually some kind of light controlling member below thelamps which shields these lamps from direct view and directs transmittedlight into directions to provide the best utilization of the light on aworking plane.

The most common type of light controlling member is a flat, orsubstantially flat, panel with cut-off prisms on its lower face. Sincethe lateral and vertical range of light from the lamps in such units isgreater than can be handled by linear type cut-off prisms, these prismsare usually in the form of cones or pyramids.

Luminaires using conical cut-off prisms provide good direct glarecontrol, but since practically no variation can be allowed in the angleof the cut-off prisms, the candlepower distribution of such luminairescannot be varied. Because of the geometry of the lamps, the longitudinaldistribution of the candlepower is rather narrow. For this reason it iscommon practice to mount the luminaires end to end or nearly so, inrows, so as to obtain even longitudinal illumination on a working plane.

Transversely, in areas where higher illumination is required, the rowsof luminaires will be spaced relatively close together. Where lowerlevels of illumination are desired, the rows of luminaires are spacedfurther apart. As the spacing is increased, however, a point is reachedwhere the illumination becomes too uneven to be acceptable. Morespecifically, there is a spacing range where Patented Dec. 9, 1969 thetotal downward output of light is sufficient to provide lower levels ofillumination, but the normal candlepower distribution is too narrow.There will be too much light in areas below the luminaires and notenough light in areas between the rows of luminaires.

It is, therefore, an object of the present invention to provide aluminaire for linear light sources, as for instance, fluorescent lamps,for general interior illumination which will provide a wider transverselight distribution.

It is another object of the present invention to provide a luminaire asset forth in the preceding paragraph which will make it possible toobtain both a low and even level of illumination across a working planeor room.

These and other objects and advantages of the invention will appear moreclearly from the following specification in combination with theaccompanying drawings in which:

FIG. 1 is a perspective view of a luminaire with a refractor lensdesigned in conformity with the present invention;

FIG. 2 is a diagrammatic bottom view of the refractor lens according toFIG. 1;

FIG. 3 illustrates the candlepower distribution of prior art luminaires,and of the luminaire according to the present invention in transverseand longitudinal directions;

FIG. 4 is a section on the line 44 of FIG. 1;

FIG. 5 illustrates the distribution of light over a working plane as.provided by a luminaire according to the present invention;

FIG. 6 is a side view of a portion of the refractor lens according toFIG. 1;

FIG. 7 is a partial bottom view of the refractor lens according to FIG.1;

FIG. 8 shows the dot-dash enclosed portion 8 of FIG. 1 on a larger scalethan FIG. 1;

FIGS. 9 and 10 are sections respectively taken on lines 9-9 and 1010 ofFIG. 8.

Referring now to the drawings in detail, FIG. 1 illustrates a luminairev10 including a fixture 11 and a refractor 12. Refractor 12 has a bottomlens portion 13 and sidewalls 14 and 15 enclosing a pair of lamps 16, 17(see FIG. 4). The ends of refractor 12 are closed by end plates 18fastened to the refractor in any convenient manner well known in theart. End plates 18 may be made of opaque plastic or another densematerial. Hinge and ledge pockets (not shown) are molded in the endplates so as to engage projections 19 carried by a fixture channel 20.Fixture channel 20 houses the electrical parts of the luminaire and iscovered by a removable cover pan 21. Elements 16 through 21 are all wellknown in the art so that a detailed description thereof does not appearto be necessary.

The prismatic structure of the bottom portion 13 of refractor 12 Withwhich the present invention is mainly concerned, carries three rows, 22,23, 24 of transverse linear cut-off prisms on its lower or lightemergent side and carries two rows 25, 26 of conical cut-off prisms inthe areas immediately beneath the lamps 16 and 17.

Sidewalls 14 and 15 carry horizontal refracting prisms 27 on the insideof the refractor and vertical diffusing prisms 28 on the outer face ofrefractor 12. The upper faces of prisms 27 direct the light downwardlyin a direction 50 and the lower faces of prisms 27 upwardly in adirection 51.

In order to illustrate the optical action of the bottom portion 13 ofthe luminaire lens 12 two longitudinal planes of light 30 and 31emanating from lamp 16 are shown. The light in plane 31 strikes thecones 32 and is spread as indicated by the emitting rays 33 and 34. Thelight in the inclined plane 30 is emitted through the row 22 oftransverse linear cut-off prisms. This light is directed into a rathercomplex pattern as will be explained in connection with FIG. 5.Considering a longitudinal fan of incident light on one small point 35of a prism 36 of row 22, this light is emitted in directions such thatit would form a trace on a working plane W as shown by a line L on FIG.5. If more small points 35 were chosen along the length of the luminairein plane 30, each would form a trace as shown in FIG. 5. Similarly, areverse trace L would be projected from the adjacent surface of thecut-off prism 36. The light intensity of these traces varies from end toend. For example, light striking the top surface of the lens bottom 13at approximately horizontal directions is largely reflected with only asmall part of the light entering and passing through the bottom 13 ofthe lens. This reduces the amount of light emitted near the end of thetraces L. Also, light transmitted through the linear cut-off prisms anddirected towards the 50 degree ends of the L traces is refracted atapproximately the critical angle so that only a small amount istransmitted while the remainder is being reflected. Between these twoextremes there is an increase in the amount of light refracted throughthe lens bottom so that the greater portion, as indicated by the solidline part of traces L and L, is transmitted quite efficiently. In otherwords, while the light from plane 30 is emitted in a range of from zeroto 50 vertically, the greater portion is concentrated in a zone between35 and 50, as can be clearly seen from the solid lines in FIG. 5.

A similar pattern of light is also projected onto working plane W bylight from lamp 17 through prisms 37 in section 23. Since refractor 12is symmetric, the same action described above occurs in reverse ordertoward the right hand side of FIG. 4.

The luminaire of FIG. 1, with the combination of prisms shown, acting asdescribed above, projects a transverse candlepower distribution as shownby curve C in FIG. 3. Curve B represents the transverse candlepowerdistribution of a luminaire similar to that of FIG. 1, but using conicalcut-off prisms only for light control instead of a combination ofconical and linear cut-off prisms. A comparison of curves B and C showsthat with the luminaire according to the invention less light is emittedvertically from approximately nadir to 30 and more light between 30 and55". This wider candl..- power distribution allows greater spacingbetween rows of luminaires with a more even illumination pattern on thework plane W.

If conical cut-off prisms were placed in the area of prisms 36, lightwould be spread vertically into a transverse zone of approximately to 50from nadir. Since this would mean that the same amount of light confinedto the much narrower 3550 zone of the linear prisms would be distributedover the wide range of from20 to 50 nadir it is obvious that theresulting transverse distribution curve would be narrower. Curves B andC have been verified by many tests made with refractor lenses.

There is a limit to the sections in which the linear cut-01f prisms canbe used. For example, incident light in a plane 38 (FIG. 4), would beemitted higher than that in plane 30. Too much light at this high anglewould make the luminaire too bright for commercial use. Therefore, thewidth of the linear prism areas 36, 38- and the placement of the linearlight sources 16, 17 must be selected so that not too much light isemitted in angles of more than 55 from nadir. The luminaire of FIG. 4 isabout optimum in its proportions and placement of linear and conicalcut-off prisms.

Luminaires using conical cut-off prisms have a certain luminosity frommost any normal lateral viewing angle. This is so since not only do theprisms emit directly a small amount of light at high angles, but theyalso emit some light that is scattered by the many facets andintersections that occur in a panel of such prisms.

This, however, is not the case with linear cut-otf prisms. In directionsnormal to their longitudinal extension they are quite dark, since theyemit no light at high angles in such directions, and since they emitpractically no scattered light because of their simple form.

Therefore, when viewing the luminaire of FIG. 1 in longitudinaldirections, the three sections 22, 23 and 24 appear unpleasantly dark.To overcome this drawback. small conical cut-off prisms 40 are disposedin the valleys of linear prisms (see FIGS. 7 to 10). These small prismsscatter suflicient light to relieve the gloomy appearance of panels 22,23 and 24. The small conical prisms 40 have a substantially ellipticalbase and are so oriented that their greatest projected area extends inlongitudinal direction of said linear cut-off prisms since most light isneeded in this direction.

Due to the decrease in the amount of light emitted near the ends offluorescent lamps 16, 17 and the opaque lamp ends and lampholders,normally luminaires appear dark near their ends. By ending the panels orrows 22. 23, 24 as shown on FIG. 7 and covering the remainder of therefractor with conical cut-off prisms 41, a break in the optical patternis made in the area where the transition from light to dark occurs.Since from most any normal viewing angle the panels or sections 25, 26with conical prisms appear of different luminosity than the sections 22,23, 24 with linear prisms 36, the change due to lamp darkness isdisguised as being normal prism pattern change.

Similarly, this break in pattern is also employed at the ends of thesidewalls as shown by prisms 42 in FIG. 6.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular constructions shown in the drawing, butalso comprises any modifications within the scope of the appendedclaims.

What is claimed is:

1. In the combination with a luminaire having a linear light source, alens comprising an extended piece of transparent material having anupper and a lower surface and extending substantially in a plane belowsaid light source. light cut-off prism means on the lower surface ofsaid lens for redirecting portions of light from said light source. saidlight cut-off prism means including a row of point apexed cut-off prismssubstantially vertically below said light source and extending in adirection parallel to the longitudinal axis of said linear light source;said light cut-off prism means further including a row of line-apexedcut-off prisms in the area of said lens laterally outwardly of andparallel to said row of point-apexed cut-off prisms, the apices of saidline-apexed cut-off prisms extending in a horizontal plane parallel tothe longitudinal axis of said linear light source and transversely toand substantially wholly laterally of the longitudinal axis of saidlinear light source, said upper surface comprising means for receiving alongitudinally oriented fan of direct light on any point laterally ofthe light source and above the active surfaces of said line-apexedcut-off prisms and for trans mitting the light from the fan of directlight received between horizontal and normal in increasingly varyingamounts to said line-apexed cut-off prisms, said lineapexed cut-offprisms constituting means for receiving said varying portions of lightand for internally reflecting varying portions thereof and fordistributing the remainder of the light not reflected downwardly inincreasingly varying portions from the inner and outer sides of areasbelow the luminaire.

2. The combination of claim 1, which includes pointapexed cut-off prismsbetween adjacent ones of said line apexed cut-off prisms for redirectinglight downwardly which would otherwise be reflected by said line-apexedprisms.

3. The combination of claim 2, in which said cut-off prisms betweenadjacent line-apexed cut-off prisms have elliptical bases with the longaxes thereof extending transversely to the axis of said linear lightsource.

4. The combination of claim 1, in which said row of line-apexed prismsends short of the ends of said lens, and point-apexed cutofi prisms aredisposed between the ends of said lens and the ends of said row of saidlineapexed prisms.

5. The combination of claim 1, wherein said lens includes side sectionsextending upwardly from said upper surface, and there are providedhorizontally extending refracting prisms on the surfaces of said sidesections which face said light source, and vertically extendingdiffusing prisms on the surfaces of said side sections which face awayfrom said light source.

6. The combination of claim 5, which includes vertically extendinglinear cut-01f prisms on the end portions of said side sections on thosesurfaces thereof which face away from said light source.

7. A lens for use in combination with a luminaire having at least onelinear light source, said lens comprising a row of point-apexed cut-offprism means substantially vertically below said linear light source andextending in a direction parallel to the longitudinal axis of saidlinear light source for cutting off light from the linear light sourceat predetermined longitudinal and transverse vertical angles below apredetermined glare zone and a row of linear cut-off prisms in the areaof said lens laterally laterally and longitudinally thereof inincreasingly varying 35 intensity from the outer and inner ends towardthe intermediate sections outwardly directed, substantially arcuatepatterns below the lens and for internally reflecting decreasinglyvarying amounts of light from the outer and inner ends toward theintermediate sections of the same patterns.

8. In combination with a luminaire having a linear light source, of alens comprising an extended piece of transparent material having anupper and a lower surface and extending substantially in a plane belowsaid light source, light cut-off prism means on the lower surface ofsaid lens for redirecting light from said light source, said lightcut-off prism means including a row of point apexed cutoff prismssubstantially vertically below said light source and also including arow of line-apexed cut-off prisms in the area of said lens and laterallyoutwardly of and parallel to said row of point-apexed cut-off prisms,the apices of said line-apexed cut-off prisms extending substantiallytransversely to the longitudinal axis of said linear light source, sidesections extending upwardly from said upper surface, horizontallyextending retracting prisms on the surfaces of said side sections whichface said light source, vertically extending diffusing prisms on thesurfaces of said side sections which face away from said light source,and vertically extending linear cut-off prisms on the end portions ofsaid side sections on those surfaces thereof which face away from saidlight source.

References Cited UNITED STATES PATENTS 2,474,317 6/1949 McPhail 240l062,737,577 3/1956 McPhail 2405l.11 3,038,065 6/1962 Frank et al 240l063,258,590 6/1966 Goodbar 240l06 3,275,822 9/1966 Wince et al. 240l06 XR3,340,393 9/1967 Frank et al 240l06 XR NORTON ANSHER, Primary ExaminerRICHARD M. SHEER, Assistant Examiner U.S. Cl. X.R. 2405 1.11

